Field of the Invention
The present invention relates to a sensor. The present invention further relates to an object positioning method, a lithographic apparatus and a method for manufacturing a device.
Description of the Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
Recent developments in lithography push the demands of the lithographic apparatus further and further, especially with respect to the positioning of different objects, such as support structures constructed to support patterning devices, substrate tables constructed to hold a substrate, and lenses in the projection system. The positioning usually needs to be done fast and accurate, where increasing the accelerations for increased speed results in larger deformations of the objects to be positioned. These deformations have a negative impact on the position accuracy. A solution is to measure the internal deformation of the object by adding position sensors measuring the position of different locations on the object relative to a reference, but as an alternative it is possible to add strain or acceleration sensors to different locations on the object. However, current strain and acceleration sensors do not have the desired resolution and/or are too sensitive to temperature and/or electromagnetic interference.